Control and Co-ordination in Plants

Giberellin in Barley Germination

Giberellins (GAs) are a class of plant hormones that play a crucial role in various aspects of plant growth and development, including seed germination. This section will describe the role of gibberellin in the germination of barley.

Mechanism of Action

Giberellins promote germination through several key mechanisms:

• Stimulation of Cell Wall Enzymes: GAs stimulate the production of enzymes like α-amylase in the aleurone layer of the barley seed.
• Mobilization of Stored Food Reserves: α-amylase breaks down starch into sugars, providing energy for the developing embryo.
• Breakage of Dormancy: GAs overcome the dormancy mechanisms in the seed, allowing germination to proceed.
• Increased Prolinase Activity: GAs can also increase the activity of prolinase, which breaks down proline, another amino acid involved in dormancy.

Experimental Evidence

The role of gibberellins in barley germination has been demonstrated through several experiments:

1. GA Treatment: Barley seeds treated with gibberellin exhibit significantly higher germination rates compared to control seeds.
2. GA Analogues: Synthetic analogues of gibberellins also promote germination, further supporting the role of GAs.
3. GA Deficiency: Seeds treated with GA antagonists (substances that inhibit GA action) show reduced germination rates.

Table Summarizing the Role of Gibberellin

Aspect	Effect of Gibberellin
Germination Rate	Increased
Starch Breakdown	Stimulated (via α-amylase production)
Dormancy Overcoming	Promoted
Prolinase Activity	Increased

In summary, gibberellin is essential for the germination of barley by stimulating the mobilization of stored food reserves and overcoming dormancy. This hormone acts by triggering the production of enzymes that break down starch and other stored nutrients, providing the energy needed for the embryo to develop.